Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2000
Publication Date: 1/1/2001
Citation: Wise, T.H., Klindt, J.M., Howard, H.J., Conley, A.J., Ford, J.J. 2001. Endocrine relationships of Meishan and White composite females after weaning and during the luteal phase of the estrous cycle. Journal of Animal Science. 79(1):176-187. Interpretive Summary: The ovary and adrenal make chemicals called hormones that affect reproduction, growth and health of animals. An understanding of how the ovary is regulated and how it interacts with the adrenal gland may lead to improved domestic animal production. Studies were conducted to determine if endocrine relationships were different in Chinese Meishan and European white composite females that would relate to ovarian function and ovulatio rates. No differences were found in gonadotrophins, inhibin, growth hormone or prolactin between the two genetic lines, but cortisol concentrations were considerably elevated in the Meishan females. Elevated cortisol concentrations noted in Meishan females may positively impact ovarian function, thus aspects of high cortisol levels as an index of stress and subsequent reduced reproductive function may have to be reevaluated in swine.
Technical Abstract: Effort has been expended on understanding the mechanisms involved with increased ovulation rates and litter size in Chinese Meishan pigs. As ovarian and uterine function are endocrine modulated, differences in endocrine function between Meishan and White breeds of European origin have been a major area of focus. Because rebreeding after weaning is the predominant method of breeding in the swine industry, indwelling jugular cannulas were placed in Meishan (n=7) and White composite (n=6) sows before weaning and blood was sampled from 3 h before to 240 h after removal from litters. Temporal differences of FSH and T3 after weaning were different between Meishan and White composite sows. Plasma cortisol concentrations were higher in Meishan sows as compared to White composite sows (P < .01), but there were not any temporal differences between breeds after weaning. Other hormones monitored (prolactin, GH, T3, IGF-1, and inhibin) were not different between breeds. In the second experiment, Meishan and White composite gilts and sows were cannulated during the luteal phase of the estrous cycle and sampled after treatments consisting of GnRH (15 and 150 ng/kg BW), ovariectomy, estradiol challenge after ovariectomy (10 ug/kg BW), and GnRH antagonist. No differences were detected in relation to sensitivity to GnRH challenge, and White composite females had elevated concentrations of gonadotropins as compared to Meishan females. Consistently elevated cortisol concentrations noted in Meishan females may positively impact ovarian function; thus, aspects of high cortisol levels as an index of stress and subsequent reduced reproductive function may have to be reevaluated in swine.